Goldman Sachs has been called in to advise MedImmune, a US pharmaceutical company, on its $15.2bn (â¬11.2bn) takeover by UK group AstraZeneca - to which Goldman provides broking services.

AstraZeneca released a statement this morning confirming the all cash $58-per share offer, which has been accepted by the MedImmune board.

A source close to the transaction said Goldman had been the financial advisor to MedImmune. Goldman was unavailable for comment.

It is rare for banks to work as an advisor on one side of a deal while holding a broking mandate from the other merger party.

Notable examples in recent years include Merrill Lynch's role advising Alliance Unichem, the pharmacy chain, on its £7bn (€10.3bn) merger with Boots while retaining the broking mandate for the UK high street company.

Merrill Lynch was appointed sole adviser to Astrazeneca, while Goldman acted as its corporate broker alongside Deutsche Bank. They replaced Merrill and Credit Suisse as brokers to Astrazeneca in 2005.

This is the UK group's largest transaction since Zeneca bought Astra in 1999 for $31.8bn, according to Thomson Financial, the data provider.

Earlier this year Astrazeneca bought Arrow Therapeutics for $142.9m. No advisors were disclosed.